Diving into the ISO OSI Network Stack Discussion
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@dafyre said in FibreChannel Switch Types:
I am trying to determine where the cohorts in the other thread were coming up with the term "iSCSI switch".
Well you can have a switch dedicated to iSCSI or as is used in many cases, you need one that is faster or handles iSCSI's needs better. You don't just use a normal switch for your SAN. But iSCSI is about iSCSI. This thread is about Fibre Channel. They two are competitors in the "use case" world and unrelated on the network.
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Fibre Channel is Layer 2, just like Ethernet. So of course you can layer TCP/IP on top of it, which is called IPFC, and then put iSCSI on top of TCP/IP. FC just replaces Ethernet in your ISO OSI stack. No one would ever do this, but you can.
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@dafyre said in FibreChannel Switch Types:
... or can it also be used for regular switching as well?
This is the bit that I don't understand. I'm only aware of switches being switches. What defines a normal switch differently from the "connects servers with FC cards" that you describe, because that sounds like normal switching to me.
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@scottalanmiller said in FibreChannel Switch Types:
@dafyre said in FibreChannel Switch Types:
I am trying to determine where the cohorts in the other thread were coming up with the term "iSCSI switch".
Well you can have a switch dedicated to iSCSI or as is used in many cases, you need one that is faster or handles iSCSI's needs better. You don't just use a normal switch for your SAN. But iSCSI is about iSCSI. This thread is about Fibre Channel. They two are competitors in the "use case" world and unrelated on the network.
That's my point... with iSCSI you can use a regular old fashioned Ethernet switch.
In general, with FibreChannel devices would use a switch made and built specifically for FibreChannel... Right? (Except for FCoE)
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@dafyre said in FibreChannel Switch Types:
That's my point... with iSCSI you can use a regular old fashioned Ethernet switch.
Ah, I'm pretty sure that you are using the term "normal" to mean "Ethernet". That's a very confusing way to use it. Ethernet and FiberChannel are both full fledged Layer 2 networking technologies. They are direct competitors and share nothing at all. A FibreChannel switch is exactly like an Ethernet switch, but switches FB not Ethernet. One is not more normal than the other. Ethernet is more popular today than FC, but that's all.
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@dafyre said in FibreChannel Switch Types:
In general, with FibreChannel devices would use a switch made and built specifically for FibreChannel... Right? (Except for FCoE)
Right FCoE is FC encapsulated over Ethernet. So that would still use an Ethernet switch. But iSCSI over TCP/IP over FC would use a FC switch. The switch is determined by the layer 2 protocol that you are using as a switch is just a handy term for a "multiport layer 2 bridge."
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@scottalanmiller said in FibreChannel Switch Types:
Ah, I'm pretty sure that you are using the term "normal" to mean "Ethernet".
Yeah. A second word I could have chosen was standard... but even then, Ethernet and FC are two different standards, lol.
Thanks for straightening my head a bit.
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@dafyre said in FibreChannel Switch Types:
... with iSCSI you can use a regular old fashioned Ethernet switch.
Can, assuming you are pumping it over Ethernet. If you put it over Token Ring, FC or other layer two option, you cannot. iSCSI is independent of this layer.
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@scottalanmiller said in FibreChannel Switch Types:
@dafyre said in FibreChannel Switch Types:
... with iSCSI you can use a regular old fashioned Ethernet switch.
Can, assuming you are pumping it over Ethernet. If you put it over Token Ring, FC or other layer two option, you cannot. iSCSI is independent of this layer.
Right. iSCSI is an IP protocol, higher up in the stack at layer 4 or 5.
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@dafyre said in FibreChannel Switch Types:
@scottalanmiller said in FibreChannel Switch Types:
@dafyre said in FibreChannel Switch Types:
... with iSCSI you can use a regular old fashioned Ethernet switch.
Can, assuming you are pumping it over Ethernet. If you put it over Token Ring, FC or other layer two option, you cannot. iSCSI is independent of this layer.
Right. iSCSI is an IP protocol, higher up in the stack at layer 4 or 5.
It's an application protocol, layer 7.
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IP is Layer 3
TCP is Layer 4
SSL is Layer 6
iSCSI is Layer 7 -
@scottalanmiller said in FibreChannel Switch Types:
@dafyre said in FibreChannel Switch Types:
@scottalanmiller said in FibreChannel Switch Types:
@dafyre said in FibreChannel Switch Types:
... with iSCSI you can use a regular old fashioned Ethernet switch.
Can, assuming you are pumping it over Ethernet. If you put it over Token Ring, FC or other layer two option, you cannot. iSCSI is independent of this layer.
Right. iSCSI is an IP protocol, higher up in the stack at layer 4 or 5.
It's an application protocol, layer 7.
What makes it Application layer instead of Session layer?
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@dafyre said in FibreChannel Switch Types:
@scottalanmiller said in FibreChannel Switch Types:
@dafyre said in FibreChannel Switch Types:
@scottalanmiller said in FibreChannel Switch Types:
@dafyre said in FibreChannel Switch Types:
... with iSCSI you can use a regular old fashioned Ethernet switch.
Can, assuming you are pumping it over Ethernet. If you put it over Token Ring, FC or other layer two option, you cannot. iSCSI is independent of this layer.
Right. iSCSI is an IP protocol, higher up in the stack at layer 4 or 5.
It's an application protocol, layer 7.
What makes it Application layer instead of Session layer?
The final layer is always application, that's where the stack has to end. A session layer communications wouldn't do anything, other than operate as a VPN - and a VPN is an incomplete stack that's running just waiting for Layer 7 to come along. iSCSI actually talks to something that isn't in the network stack, and only L7 can do that. iSCSI is the same as HTTP, SMTP, XMPP, RTP and so forth.
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Remember that nothing about iSCSI is sessions related, it's not part of the networking, its the payload from the application.
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@scottalanmiller said in FibreChannel Switch Types:
Remember that nothing about iSCSI is sessions related, it's not part of the networking, its the payload from the application.
How is it not session level? it's communication between two hosts.
If SQL belongs at the session level, then so would iSCSI.
https://blogs.cisco.com/cloud/an-osi-model-for-cloud -
@dafyre said in FibreChannel Switch Types:
@scottalanmiller said in FibreChannel Switch Types:
Remember that nothing about iSCSI is sessions related, it's not part of the networking, its the payload from the application.
How is it not session level? it's communication between two hosts.
No it is not, it is the application protocol consumed by the initiator.
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@dafyre said in FibreChannel Switch Types:
If SQL belongs at the session level, then so would iSCSI.
https://blogs.cisco.com/cloud/an-osi-model-for-cloudI don't agree with CIsco and their marketing. That does not match the actual OSI stack. iSCSI is the final deliverable of the network, it is the application "end user" product here... the payload. It doesn't interact with the stack.
SQL in that stack is misleading, it isn't like anything else there. It's many levels higher, because it obviously is L8 because you type it directly, which you never do even with L7.
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So that means you would put things like NFS, and NetBios at the application layer too? (pulling again, from the Cisco page for reference).
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@dafyre said in FibreChannel Switch Types:
So that means you would put things like NFS, and NetBios at the application layer too? (pulling again, from the Cisco page for reference).
Of course, which is where they are accepted by the industry to be and always have been. Remember that Cisco calls when they do Ethernet too, but isn't part of the standard. Cisco and standards are oil and water. That's the last place you should be looking for how networking works, they have their own agenda, they own definitions and their own compatibility.
https://en.wikipedia.org/wiki/Application_layer
iSCSI is layer 7. SQL is not part of the network at all but you can call it L8, the layer directly above the network stack. But if you've ever worked with a database, it is really obvious that SQL is a language that humans work in, so is above the stack. Just like BASH is not part of the network stack. Or PowerShell. Of a text based video games.... those are applications. Applications are above the application layer of the OSI stack, not part of it.
